1 files changed, 144 insertions, 0 deletions
diff --git a/debian/bash.preinst.c b/debian/bash.preinst.c
new file mode 100644
index 0000000..ff22653
--- /dev/null
+++ b/debian/bash.preinst.c
@@ -0,0 +1,144 @@
+/* Copyright (c) 1999 Anthony Towns
+ * Copyright (c) 2000, 2002 Matthias Klose
+ *
+ * You may freely use, distribute, and modify this program.
+ */
+
+// Don't rely on /bin/sh and popen!
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+/* XXX: evil kludge, deal with arbitrary name lengths */
+#ifndef PATH_MAX
+#define PATH_MAX 4096
+#endif
+
+int check_predepends(void)
+{
+    pid_t child;
+
+    switch(child = fork()) {
+      case -1:
+        /* fork failed */
+        return EXIT_FAILURE;
+
+      case 0:
+        /* i'm the child */
+        {
+            execl( "/usr/bin/dpkg", "/usr/bin/dpkg",
+                   "--assert-support-predepends", NULL );
+           _exit(127);
+        }
+
+      default:
+        /* i'm the parent */
+        {
+            int status;
+            pid_t pid;
+            pid = wait(&status);
+            if (pid == child) {
+                if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
+                    return EXIT_SUCCESS;
+                }
+            }
+        }
+    }
+    return EXIT_FAILURE;
+}
+
+char *check_diversion(void)
+{
+    pid_t child;
+    int pipedes[2];
+
+    if (pipe(pipedes))
+	return NULL;
+
+
+    switch(child = fork()) {
+      case -1:
+        /* fork failed */
+	close(pipedes[0]);
+	close(pipedes[1]);
+        return NULL;
+
+      case 0:
+        /* i'm the child */
+        {
+	    if (dup2(pipedes[STDOUT_FILENO], STDOUT_FILENO) < 0)
+		_exit(127);
+	    close(pipedes[STDIN_FILENO]);
+	    close(pipedes[STDOUT_FILENO]);
+            execl( "/usr/sbin/dpkg-divert", "/usr/sbin/dpkg-divert",
+                   "--list", "/bin/sh", NULL );
+           _exit(127);
+        }
+
+      default:
+        /* i'm the parent */
+        {
+	    static char line[1024];
+	    FILE *fd;
+
+	    close (pipedes[STDOUT_FILENO]);
+	    fcntl (pipedes[STDIN_FILENO], F_SETFD, FD_CLOEXEC);
+	    fd = fdopen (pipedes[STDIN_FILENO], "r");
+
+	    while (fgets(line, 1024, fd) != NULL) {
+		line[strlen(line)-1] = '\0';
+		break;
+	    }
+	    fclose(fd);
+	    return line;
+        }
+    }
+    return NULL;
+}
+
+const char *msg =
+  "As bash for Debian is destined to provide a working /bin/sh (pointing to\n"
+  "/bin/bash) your link will be overwritten by a default link.\n\n"
+  "If you don't want further upgrades to overwrite your customization,\n"
+  "please read /usr/share/doc/bash/README.Debian for a more permanent solution.\n\n"
+  "[Press RETURN to continue]";
+
+int main(void) {
+    int targetlen;
+    char target[PATH_MAX+1], answer[1024];
+
+    if (check_predepends() != EXIT_SUCCESS) {
+	printf("\nPlease upgrade to a new version of dpkg\n\n");
+	return EXIT_FAILURE;
+    }
+    targetlen = readlink("/bin/sh", target, PATH_MAX);
+    if (targetlen == -1) {
+	// error reading link. Will be overwritten.
+	puts("The bash upgrade discovered that something is wrong with your /bin/sh link.");
+	puts(msg);
+	fgets(answer, 1024, stdin);
+	return EXIT_SUCCESS;
+    }
+    target[targetlen] = '\0';
+    if (strcmp(target, "bash") != 0 && strcmp(target, "/bin/bash") != 0) {
+	char *diversion = check_diversion();
+
+	if (diversion == NULL)
+	    return EXIT_FAILURE;
+	// printf("diversion: /%s/\n", diversion);
+	if (strcmp(diversion, "") != 0)
+	    // link is diverted
+	    return EXIT_SUCCESS;
+	printf("The bash upgrade discovered that your /bin/sh link points to %s.\n", target);
+	puts(msg);
+	fgets(answer, 1024, stdin);
+	return EXIT_SUCCESS;
+    }
+    return EXIT_SUCCESS;
+}